Fabricated finned tubing



Oct. 25, 1966 E. P. HABDAS 3,280,851

FABRI CATED FINNED TUBING Filed May 10, 1965 FIGS INVENTOR.

EDW RD P. HABDAS ATTORNE S United States Patent Oflice 3,280,851Patented Oct. 25, 1966 3,280,851 FABRICATED FINNED TUBING Edward P.Habdas, Dearborn, Mich, assignor to Calumet & Hecla, Inc., Allen Park,Mich., a corporation of Michigan Filed May 10, 1965, Ser. No. 454,587Claims. (Cl. 138-154) This is a continuation-in-part of applicationsSerial Nos. 201,511 and 201,515, both filed June 11,1962, now US.Patents Nos. 3,240,177 and 3,240,042. respectively.

The present invention relates to fabricated tubing.

It is an object of the present invention to provide tubing in the formof a continuously wound strip of U-shaped cross-section in which theside flanges of the U have been tapered to diminishing thicknessprogressively in such a way that the tapered edge flanges cause thestrip to wind into a coil.

It is a further object of the present invention to provide a tube fromU-shaped strip having a web and edge flanges in which the edge flangesare tapered to diminishing thickness outwardly of the web, and in whichthe outer surfaces of the flanges are bonded together to form a unitarytubing having an integral flange formed thereon.

It is a further object of the present invention to provide a finned tubein which the fins are produced by bonding together outer edges oflaterally extending and tapered flanges to produce a unitary flangewhich is also tapered to diminishing thickness outwardly of the tubewall.

It is a further object of the present invention to provide finned tubingproduced from U-shaped strip having a web and relatively Wide flangesextending outwardly from the web, the flanges being of suflicient heightto produce eflicient heat transfer fins, the outer surfaces of adjacentconvolutions of the strip being bonded together.

It is a further object of the present invention to provide tubing formedof U-shaped strip having a central web and laterally turned flanges, theflanges being tapered to diminishing thickness outwardly of the web andbonded together, one of the flanges being relatively wide and operativeto perform efliciently as a heat transfer fin, the other flange beingrelatively narrow and bonded throughout its lateral surface area to theportion of the relatively wide flange adjacent the web of the U-strip.

It is a further object of the present invention to provide flexibletubing formed of generally U-shaped strip having a central Web andlaterally extending flanges tapered to be of diminishing thicknessoutwardly of the web, the strip being coiled into a tight helicalconfiguration in which the outer surfaces of the flanges of adjacentconvolutions are bonded together in a helical zone extending inwardlyfrom the outer edges of the flanges for a distance substantially lessthan the full width of the flanges.

It is a further object of the present invention to provide tubing asdescribed in the preceding paragraph in which the portions of the flangeintermediate the helically extending bonded zone and the webs diverge.

Other objects and features of the invention will become apparent as thedescription proceeds, especially when taken in conjunction with theaccompanying drawings, illustrating preferred embodiments of theinvention, Wherein:

FIGURE 1 is a diagrammatic view illustrating a preferred method ofproducing the tubing disclosed herein.

FIGURE 2 is a sect-ion on the line 22, FIGURE 1.

FIGURE 3 is a section on the line 33, FIGURE 1.

FIGURE 4 is an enlarged section of a portion of FIG. URE 1.

FIGURE 5 is an an enlarged sectional view of a portion of FIGURE 1.

FIGURE 6 is a fragmentary section through a U- shaped strip of differentproportion.

FIGURE 7 is a view of the strip shown in FIGURE 6 after its flanges havebeen tapered.

FIGURE 8 is a fragmentary sectional view of tubing produced fromU-shaped strip of the configuration illustrated in FIGURE 7.

FIGURE 9 is a longitudinal sectional view similar to FIGURE 8, showinganother embodiment of the invention.

FIGURE 10 is a longitudinal sectional view similar to FIGURE 8, showingyet another embodiment of the present invention.

The present invention includes tubing, preferably metal tubing, of anyconvenient size, but is particularly useful in the production ofrelatively large light-walled tubing such for example as is used inirrigation fields. Tubing of this type is generally transported manuallyfrom place to place and since it is not subjected to any relativelygreat internal pressure, it may be relatively thin-walled.

However, it is necessary for tubing of this type to be sufiicientlystiff so as to permit its transportation without alteration of itsgenerally cylindrical configuration.

As seen in FIGURE 1, such tubing is indicated generally at 10 Where itis shown as located on a rotating mandrel 12. The portion of the tubingseen at 10a includes a helical flange, fin or bead 14, the nature andmethod of production of which will subsequently be described. For thepresent however, it is to be noted that this continuous helical flangeconstitutes a stiffening means which renders a substantial length of thetubing selfsupporting, at least sufficiently so as to permit readytransportation. The fin 14 as previously described, may be relativelylow or in fact may be flattened down against the tube, as willsubsequently be described. Alternatively, it may be relatively high soas to constitute an efficient heat transfer means.

If desired, and as a modification of the tubing as illustrated, theflange, fin 0r bead 14 may be bent over and flattened against the outercylindrical surface of the tub ing as indicated at 1412, as bestillustrated in FIGURE 5. It will of course be apparent that for maximumstiffness the flange 14 should be left to extend generally radially asdesignated in the zone 10a. Where such stiffness is not required theflange may be bent down as indicated at 1411.

The nature of the tubing is best understood from a description of themethod of producing it. As best seen in FIGURE 1, a continuous flatstrip 20 is advanced for example from a storage reel, through a formingstation designated 21 in which inner forming rolls 22 and 24 are carriedby a support 26 and cooperate with outer forming rolls 27 and 28respectively. The advance of the fiat stock through the forming station21 results in forming this trip into U-shaped cross-section comprising acentral web having edge portions bent upwardly into the indi vidualflanges 30 and 32, as best seen in FIGURE 2. Since the operation carriedout at the forming station 21 is essentially a bending operation, itwill of course be apparent that the bent up flanges 30 and 32 are ofuniform thickness from edge to edge, and that accordingly, the strip 20as it advances beyond the forming station 21, remains essentially a flatstrip.

At a forming station 34, which is directly adjacent the rotating mandrel12, means are provided for edge thinning or tapering the edge flanges 30and 32 to the crosssection illustrated at 30a and 32a in FIGURE 3. Thistapering operation is accomplished by edge thinning rolls 35 and 36operating against a stationary anvil 38. It will of course be understoodthat instead of a solid anvil 38, a block similar to the support 26provided with inner rolls opposed to the outer rolls 35 ad 36 may beprovided.

It is to be noted at this time that the rolling operation performed bythe rolls 35 and 36, together with the anvil 38 or inner rolls ifpreferred, is an operation in which the edge flanges are tapered byrolling them longitudinally in the longitudinal direction of the strip.Elongation of material rolled in one direction takes place substantiallycompletely in the direction of roll and the amount of elongation bears adirect relationship to the amount of reduction in thickness resultingfrom the rolling operation. Accordingly, the relatively thin outer edgesof the flanges become longitudinally elongated as compared to the web ofthe strip, and this causes the strip as a Whole to tend to coil as seenin FIGURE 1. This coiling of the strip is guided so that the strip coilshelically about the mandrel into a tight helical configuration with theouter surfaces of the tapered flanges, or portions thereof,.abutting.Portions of the outer surfaces of the flanges are permanently bondedtogether as by Welding.

In order to carry out this operation most efficiently, the anvil 38 andthe thinning rolls 35 and 36 are located as closely as possible to thezone of tangency between the advancing generally flat strip 20 with thecylindrical surface of the mandrel 12. Thus, referring to FIGURE 1 itwill be observed that the rolls 35 and 36 are in alignment with the axisof the mandrel and hence, are not located directly opposite each otheracross the width of the advancing strip 20. This arrangement tends toform the strip into a helical path and its exact position is determinedby engagement with the rotating mandrel.

In FIGURES 1 the roll 36 operates with the anvil 38 to form the righthand flange 32 into the required tapered form illustrated at 32a bydirect engagement with opposite sides thereof. The roll 35 however,cooperates with the anvil to receive therebetween not only the flange 30of the advancing strip, but also the tapered flange 32a, as it advancesaround to start the second convolution.

Instead of having the roll 35 operate to taper the flange 30 against theanvil 38 through the previously tapered flange 32a as suggested in fulllines in FIGURE 1, it may operate in advance of the full line position,as for example in the dotted line position designated 35a, in which caseit will impart a taper to the flange 30 to the shape illustrated at 30a,FIGURE 3, prior to engagement of the flange 30a with the flange 32a ofthe preceding convolution. Roll 36 is then preferably operated in theposition illustrated in dotted lines at 36a.

In addition to edge thinning or tapering the flanges 3t) and 32 to theconfiguration illustrated at 30a and 32a, the anvil 38 and the roll 36serve as abutment means insuring continuous advance of the helicallycoiled strip on the rotating mandrel. Since the direction of advance ofthe strip as it engages the surface of the mandrel is different from theinstantaneous direction of movement of the engaged surface of themandrel, it will of course be apparent that the tube assembly is ineffect sliding continuously longitudinally. I

Means are provided for bonding the confronting surfaces of the taperedflanges 30a and 32:: so as to form the helically wound strip into acontinuous sealed tube. This means is illustrated in FIGURE 1 as takingthe form of a pair of welding electrodes 40 and 42 shaped to press theflanges 30a and 32a into firm contact and to effect a weld by elevatingthe temperature of the flanges by current passing therethrough.Obviously, the welding action may be controlled by the pressure exertedon the flanges by the electrodes 40 and 42, the angular extent of theelectrodes, the Welding current applied to the electrodes, and the rateof advance of the strip 20. It will further be understood that thewelding operation as illustrated and described herein is merely oneconvenient plied by rotating the mandrel and drawing the strip throughthe rolls 22, 24, 27, 28, and 36. However, since the material may inmost cases be relatively thinwalled, it is ordinarily desirable toeffect powered rotation of certain of the rollers, particularly therollers 35 and 36. In some cases the mandrel 12 may be rotated so as tomaintain tension in the strip.

While the present invention is particularly applicable to the productionof metal tubing for example as aluminum or aluminum alloy tubing, it isapparent that the tubing may be of other metals or of plastic, in whichcase elements and 42 may simply be heated elements for effecting thermalbonding of the fins.

Referring now to FIGURES 6-8 there is illustrated another embodiment ofthe invention. In this case a strip is bent to U-shaped configuration soas to comprise .a web 54 and flanges 56 and 58. The flanges 56 and 58may be rolled longitudinally by mechanism equivalent to that illustratedin FIGURE 1 so as to produce tapered flanges 56a and 58a. This U-shapedcross-sectional tube is coiled around the mandrel in the same manner asdis closed in FIGURE 1, to produce the tubing illustrated at 60 inFIGURE 8 where the tapered flanges 56a and 58a are bonded togetherthroughout their height to produce correspondingly tapered relativelyhigh heat transfer fins 62. -It will be observed that the fins 62 tapersubstantially uniformly from the base or root to the outer edge thereof.This arrangement provides for maximum utilization of material since thecross-sectional thickness of the fin reduces as the necessity for heatconduction is reduced by the loss of heat from the surface of the fin.More over, the tubing illustrated in FIGURE 8 provides for maximumstrength of bond since the bond between the outer surfaces of the edgeflanges may occupy a relatively method of effecting a satisfactorybonding of the strip.

If it is desired to eliminate the generally radially outwardly andhelically extending fin 14, it may be rolled down to the configurationillustrated at 14b in FIGURE 5 by a flattening roller 50 locatedadjacent the mandrel 12 in position to engage the flange as it advances.

Advance of the strip onto the mandrel may be accomgreat area. Finally,the construction illustrated in FIG- URE 8 is of great utility in thatthe tapered flanges in addition to serving as eflicient heat transferfins, constitute structural portions of the tubing giving the tubingmechaical strength without requiring a wall thickness in excess of thatrequired to withstand anticipated pressure difi'erenges between fluidwithin the .tube and outside of the tu e.

Referring now to FIGURE 9 there is illustrated yet another embodiment ofthe invention in which the tube 64 is formed from strip having a web 66,a relatively high tapered edge flange 68, and a relatively narrow edgeflange 70. The outer surface of .the flange 70 is welded or otherwisebonded to that portion of the outer surface of the flange 68 adjacent tothe web- 66. With this arrangement most eflicient utilization ofmaterial is employed since the relatively high flange 68 forming the finmay be designed for most eflicient heat transfer, Whereas the bondbetween adjacent convolutions requires only the relatively low or narrowflange 70 for satisfactory integrity of the tubing.

'In FIGURE 10 there is illustrated yet another embodiment of theinvention which is characterized particularly in flexibility of thecompleted product. In this case the tubing 72 is formed of a generallyU-shaped strip which when coiled has an inner relatively narrow web 74,outwardly diverging flange port-ions 76 terminating in outer edgeportions 78 adapted to abut in surface to surface engagement asillustrated. The outer edge portions of the flanges or fins are suitablybonded together and the inwardly diverging flange portions providesubstantial lateral and some longitudinal flexibility or stretchabilityof the compieted tube.

The drawings and the foregoing specification eonstitute a description ofthe improved fabricated finned tubing and apparatus for making the samein such full, clear, concise and exact terms as to enable any personskilled in the ant to practice the invention, the scope of which isindicated by the appended claims.

What I claim as my invent-ion is:

1. Thin-walled tubing formed from flexible fiat strip and consisting inits entirety of a single continuous helica-lly wound strip having bothedge portions turned to form the strip to substantially U-shapedcross-section having edge flanges extending in the same direction fromsaid strip substantially perpendicular therefrom and radially of thetubing, said flanges being of substantially uniformly tapered thicknessfrom the inner to the outer edge thereof, the outer surfaces of saidflanges being substantially fiat surfaces in substantiallysurfaceto-surface contact and bonded together throughout the area ofcontact.

2. Tubing as defined in claim 1 in which at least one of said flanges isof a width sufiicient to form an eflFective heat transfer fi-n.

3. Tubing as defined in claim 1 in which both of said flanges are of aWidth suflicient to form an efiective heat transfer fin.

4. Tubing as defined in claim 1 in which said flanges are of substantialequal width and taper at their free edges to substantially knife-edges.

5. Tubing as defined in claim 4 in which said flanges are bondedtogether substantially throughout their entire width several timesgreater than the thickness of the wall outer surfaces to produce acontinuous sealed joint of a thickness of the strip from which thetubing is produced.

References Cited by the Examiner UNITED STATES PATENTS LAV ERNE D.GEIGER, Primary Examiner.

C. HOUCK, Assistant Examiner.

1. THIN-WALLED TUBING FORMED FROM FLEXIBLE FLAT STRIP AND CONSISTING INITS ENTIRETY OF A SINGLE CONTINUOUS HELICALLY WOUND STRIP HAVING BOTHEDGE PORTIONS TURNED TO FORM THE STRIP TO SUBSTANTIALLY U-SHAPEDCROSS-SECTION HAVING EDGE FLANGES EXTENDING IN THE SAME DIRECTION FROMSAID STRIP SUBSTANTIALLY PERPENDICULAR THEREFROM AND RADIALLY OF THETUBING, SAID FLANGES BEING OF SUBSTANTIALLY UNIFORMLY TAPERED THICKNESSFROM THE INNER TO THE OTHER EDGE THEREOF, THE OUTER SURFACES OF SAIDFLANGES BEING SUBSTANTIALLY FLAT SURFACES IN SUBSTANTIALLYSURFACE-TO-SURFACE CONTACT AND BONDED TOGETHER THROUGHOUT THE AREA OFCONTACT.